In any event, the business of what Watson had called “working out the details” continued to be a somewhat sticky one. The experiments went on all summer as Bell and Watson juggled components in an attempt to improve reception. They could hear each other’s voices, but only rarely could they distinguish fragments of sentences, isolated phrases, or scattered words. Day after fruitless day they found themselves at a loss as to what to try next. Bell’s problems, moreover, were aggravated by other factors. He was deeply involved in drafting specifications and claims for patent rights, foreign and domestic, on both the harmonic telegraph and the telephone[Bell's basic U.S. Patent No. 174,465, covering the telephone–"The method of, and apparatus for, transmitting vocal or other sounds telegraphically, as herein described, by causing electrical undulations similar in form to the vibrations of the air accompanying the said vocal or other sounds, substantially as set forth"–was granted on March 7, 1876.]; hence much of his time was consumed in paper work. Then too, his health took a turn for the worse during the hot summer months. And finally, he was beset by financial difficulties. In his zeal to perfect the telephone he had abandoned all his teaching engagements, and now his funds were running low. While his sponsors had agreed to cover his laboratory expenses, no provision had been made for personal expenses. Bell was reluctant to request further assistance, for although both men now saw the potential of the telephone, Sanders had already invested large sums in Bell’s work without return, and Bell’s relationship with Hubbard was even more sensitive. For he hoped, when he became more solvent, to marry Hubbard’s daughter, Mabel.

Seeing no other solution to his predicament, Bell returned briefly to his work with the deaf, lecturing to student teachers and building up a new clientele of private pupils. Toward the end of 1875 his circumstances improved. He was able to move his apparatus from the Williams shop, where it had been eyed by increasing numbers of inquisitive strangers, to private quarters of his own in 5 Exeter Place, Boston. There, through the winter and early spring, Bell continued his experiments and evolved a new and modified transmitter, abetted by a variable battery current. On the night of March 10, 1876, just nine months after Bell’s harmonic telegraph receiver gave out its promising twang, his telephone pronounced its first complete and intelligible sentence. Watson, who had continued to assist Bell faithfully, constructing his apparatus and working with him night after night no less assiduously than at the workshop in Court Street, was on the receiving end this time, and he recorded the event:

It made such an impression upon me that I wrote that first sentence in a book I have always preserved. The occasion had not been arranged and rehearsed as I suspect the sending of the first message over the Morse telegraph had been years before, for instead of that noble first telegraphic message—“What hath God wrought?”—the first message of the telephone was: “Mr. Watson, come here, I want you.” Perhaps if Mr. Bell had realized that he was about to make a bit of history, he would have been prepared with a more sounding and interesting sentence.

Thereafter events moved swiftly. In June, 1876, Bell exhibited his apparatus at the Centennial Exposition in Philadelphia, where he won prizes for both the telephone and his harmonic telegraph. Among the judges were Joseph Henry; the Emperor Dom Pedro of Brazil, who exclaimed, “My God, it talks”; and Sir William Thomson (Baron Kelvin), who later called the telephone “the most wonderful thing [he had seen] in America.” There followed a series of demonstrations in both the United States and Canada, with lectures by Bell and gradually lengthening lines of communication. The demonstration circuits began with two miles of wire between Bell’s home in Brantford and the neighboring town of Mount Pleasant; by the spring of 1877 a line had been set up from New Brunswick, New Jersey, to New York City, a distance of more than thirty miles. (The wires were leased, for these occasions, from Western Union.) The reactions of audiences ranged from incredulity, through enthusiasm, to skepticism. Some saw in the telephone only an ingenious novelty. Shortly after the Philadelphia Centennial Exposition, the New York Tribune commented editorially in this vein:

Of what use is such an invention? Well, there may be occasions of state when it is necessary for officials who are far apart to talk with each other, without the interferences of an operator. Or some lover may wish to pop the question directly into the ear of a lady and hear for himself her reply, though miles away; it is not for us to guess how courtships will be conducted in the twentieth century. It is said that the human voice has been conveyed by this contrivance over a circuit of sixty miles. Music can be readily transmitted. Think of serenading by telegraph!